Apparatus for heat treating bulk material



APPARATUS FOR HEAT TREATING BULK MATERIAL Fil'ed Feb. 23, 1954 H. RUSCHE July 16, 1957 3 Sheets-Sheet 1 y 1957 H. RuscHE 2,799,489

' APPARATUS FOR HEAT TREATING BULK MATERIAL Filed Feb. 2-15, 1954 3 Sheets-Sheet 2 H. RUSCHE 2,799,489

APPARATUS FOR HEAT TREATING BULK MATERIAL- 5 Sheets-Sheet 3 July 16, 1957 Filed Feb 25, 1954 United States Patent APPARATUS FOR HEAT TREATING BULK MATERIAL Hans Rusche, Wulfrath, Germany Application February 23, 1954, Serial No. 412,635

Claims priority, application Germany February 21, 1953 11 Claims. (Cl. 263-32) The present invention relates to a method and to apparatus for the heat treatment, for example, drying, calcining, burning or sintering, of bulk material, in pieces or in granulated form, such as chalk, dolomite, cement, ore or the like. 7

Methods directed to this end are known in which the heat treatment is carried out in two successive stages, the bulk material 'being first supplied to a shaft furnace of annular cross-sectional shape and having good heatconserving properties, after which the material which has been preheated in the annular shaft furnace, is dis charged from the latter and conducted to a finishing furnace or to a furnace in which the heat treatment is completed under different temperature conditions. Such methods, however, have the disadvantage that the combustion gases leaving the finishing furnace are at a comparatively high temperature and also that the bulk material leaving the annular shaft furnace is highly heated sothat considerable stresses are imposed on the parts connecting the furnaces. Moreover, the known forms of apparatus do not provide for uniform heating up of the material passing through the shaft furnace and thus satisfactory control of the final stage is difficult to attain.

These drawbacks are substantially eliminated by the present invention in that the combustion gases leaving the finishing furnace are supplied tothe shaft furnace from below and above the annular furnace discharge outlet' in a uniformly distributed fashion, and are then passed upwardly through this shaft furnace in order to leave this from an upper part. In this way, a particularly uniform heating up of the bulk material descending through the shaft furnace is obtained, allied with an optimum utilization of the heat. Thus, for example, it is also possible to treat material in granulated form, this material being preheated so slowly that it does not disrupt.

The carrying out of the heat treatment in a' shaft furnace and in a subsequent finishing furnace enables the process to be carried out in a particularly economical fashion by making full size, in the shaft furnace; of the heat of the waste gases from the finishing furnace. Furthermore, particularly in the calcination of limestone, a uniformly calcined end product can be obtained, if the preheating in the shaft furnace is carried out at a temperature which is preferably above the dissociation temperature of the limestone, whilst the final heating takes place at a temperature which is only slightly above the dissociation temperature of the carbonate, i. e. at a temperature which can be exactly controlled in the finishing furnace.

Moreover, when sintering dolomite, magnesite, ore or cement flour or granules, the heat treatment in the finishing furnace may be' carried out with a comparatively minor amount of oxygen, i. e. an. amount only sufiicient for effecting the final treatment, whereas the preheating of the material in the shaft furnace may be effected with the waste gases from a rotary tubular furnace until the Patented July 16, 1957 commencement of the sintering or the point at which the bulk material ceases to lose its fluent nature.

Different fuels, suited to the respective furnaces, may be used in the shaft and finishing furnaces, and the waste gases leaving the finishing furnace can be additionally heated before entering the shaft furnace. Furthermore, it is of advantage to supply the waste gases from the finishing furnace to the annular outlet from the shaft furnace through a supply channel which is directly connected to the finishing furnace.

The novel apparatus of this invention, comprising an annular shaft furnace having a discharge ring, a finishing furnace beneath the annular discharge outlet from the shaft furnace and above the discharge ring, consequently has an annular space through which the gas flowing out of the finishing furnace is uniformly distributed into the shaft furnace in order to fiow upwardly through the latter.

The discharge ring is preferably freely mounted over a hopper which guides the material dropping from the ring to the finishing furnace. This hopper may be provided with radial supporting brackets which carry the discharge ring, the waste gases leaving the finishing furnace passing in counterflow through the material in the hopper.

Preferably, moreover, either the hopper is provided for rotation relatively to the stationary annular shaft furnace or the latter, or its outer casing, is rotatable and the hopper fixed. The annular channel for receiving and distributing the waste gases from the finishing furnace, which is arranged beneath the outlet from the shaft furnace, may be directly connected to the finshing furnace, passing round the hopper in so doing.

Further features of the invention are disclosed in the accompanying drawings, in which various embodiments of the invention are illustrated by way of example and in which:

Figure l is a longitudinal section through an annular shaft furnace having an adjoining rotatable hopper.

Figure 2 shows apparatus similar to Figure 1 with an adjoining rotary tubular furnace, this view being taken from the side and having a part in section.

Figure 3 shows a rotary annular shaft furnace with an adjoining hopper, this also being in the form of a longitudinal section.

Figure 4 shows an apparatus similar to that of Figure 3 with an adjoining shaft furnace, partly in section.

Figure 5 shows the lower part of a hopper and the adjoining combustion chamber,

Figure 6 shows an annular shaft furnace with a downwardly extended furnace core, a rotatable hopper and an annular channel directly connected to an adjoining rotary tubular furnace, the parts being seen in longitudinal section, and

Figure 7 shows a similar arrangement but with a fixed furnace core and hopper and a rotatable casing for the shaft furnace, again in longitudinal section.

in the embodiment of the invention illustrated in Figure 1, bulk material in the form of pieces or granules passes through a hopper 1 into an annular shaft furnace 2 which has an outer casing 3 and a core 4. This furnace is provided with brackets 5 by which it is mounted on supports 6.

The furnace 2 is provided with an annular discharge outlet 7 below which is arranged a hopper 8 having radial supporting webs 9 carrying a discharge ring 1% which has a wedge-form protuberance 11. The discharge ring is so arranged that a free annular space 12 remains between the outer casing of the hopper 8 and this discharge ring, so that the material issuing from the outlet of the shaft furnace falls partly through this annular free space and partly through the inner opening 13 of the discharge ring and thence into the hopper 8. The waste gases from a finishing furnace 2-4 (see Figure 2) pass in countercurrent to the material 14 in the direction of the arrows and in part pass through the inner opening 13 of the discharge ring and partly through the annular space 12 below the furnace discharge opening 7, to pass thence uniformly into the shaft furnace so as to ascend through this and to leave it through an outlet 15.

The hopper 8 is provided with brackets 16 by means of which it carries wheels 17 which are mounted so as to revolve on a circular rail 18. The rotation of the hopper is efiected from a motor 19 through a spur pinion 20 which engages with the toothed periphery 21 on the hopper 8. The latter is fluid-tightly sealed to the shaft furnace and to the finishing furnace by sand or water seals, such 'as shown at 22.

The material falling from the hopper 8 passes, as shown in Figure 2, through a pipe connection 23 into a rotary tubular finishing furnace 24.

The apparatus illustrated in Figure 3 generally corresponds in its construction to that described in connection with Figure 1, but in this case, the hopper 25 has brackets 27 which are fixedly seated on the supporting base 23. The annular shaft furnace 2 is rotatable relatively to this fixed hopper, the brackets of the furnace casing 3 carrying wheels 29 running on a circular track 3%). The shaft furnace 2 is further provided with a toothed crown 31 with which engages a spur wheel 32 driven by a motor 33. As in Figure 2, a rotary tubular furnace or, as illustrated in Figure 4, a further annular shaft furnace 34 with an outlet 35', can be used as a finishing furnace for preheating the gases for the shaft furnace 2 and, if appropriate, for effecting completion of the heat treatment of the material 14.

As illustrated in Figure 5, the hopper 25, and its radial supporting webs 26, may lead to a combustion chamber 36 in which the waste gases ascending from the finishing furnace are heated. This heating is effected by burners 36 which are connected to an annular channel 38 and are controlled by valves 39.

In the embodiment of the invention illustrated in Figure 6, the core 40 of the shaft furnace is provided at its lower end with a conical projection 41 having a cone angle such as to provide the desired inclination to the fluent material.

In this case a rotary tubular furnace 24 has been illustrated as the finishing furnace, this being by way of example. The waste gases ascending from this are introduced directly into an annular channel 43 through a conduit 4-2, the inner boundary of the channel 43 being formed by the layer of material which flows over the conical projection 41.. The gases pass through this layer of material from all sides and uniformly into the annular shaft furnace 2, flow upwardly therethrough and leave through the outlet 15. In this embodiment the hopper 8 is rotatably mounted in a similar way to that used in the embodiment of Figure 1, the discharge ring it) carried by the hopper 8 being arranged beneath an annular gap 44 into which the material loosened from the conical projection 41 falls.

In the embodiment illustrated in Figure 7, which is similar to that of Figure 6, the hopper 45 is fixed and has brackets 46 which carry the core 47 of the furnace with its conical projection 48 and the discharge ring 49. The furnace casing 50 is rotatable relatively to these immobile parts, brackets 51 mounted on the casing carrying wheels 52 turning on a circular track 53. The furnace casing is rotated by means of a motor 54 operating a pinion 55 meshing with a toothed crown 56.

The annular shaft furnace, the discharge ring, the adjoining hopper, and the other parts leading to the finishing furnace are preferably made of refractory material or are lined With such material, for example fireclay.

I claim:

1. Apparatus for heat treating bulk material, said apparatus comprising an annular shaft furnace for prcliminary heat treatment of said bulk material; a finishing furnace to which said preheated bulk material is fed for final treatment therein, said finishing furnace being a rotary furnace; said shaft furnace having an annular outer casing and a furnace core defining an annular shaft furnace space therebetween, in which the bulk material is preliminarily treated by gases entering through the lower open end of said annular space and flowing upwardly in counter current to the flow of the bulk material; a discharge ring concentrically arranged to the axis of said shaft furnace and at a distance from said lower open end, said discharge ring serving as support for the column of bulk material descending by gravity through said annular shaft furnace space; means for conducting said gases from said finishing furnace to a space surrounding the exposed surface of that portion of said bulk material column disposed between said lower open end and said discharge ring; means for effecting relative movement between said discharge ring and at least one of the two parts defining said annular shaft furnace space; a substantially funnel shaped discharge hopper concentrically located below said discharge ring and fastened thereto, the upper end of said hopper having an inner diameter larger than the outer diameter of said discharge ring, so as to provide "a passage through which material discharged from the outer edge of said discharge ring by said relative movement falls into said hopper; and conduit means connected to the lower end of said hopper through which said preliminarily treated bulk material passes into said finishing furnace.

2. Apparatus according to claim 1 wherein said dis charge ring has a circular opening located below said shaft furnace core for dividing the flow of material from said discharge ring into two concentric streams.

3. Apparatus according to claim 2 wherein said annular discharge ring is provided with a circular protrusion of wedge shaped cross section to facilitate division of discharged material into said two streams.

4. Apparatus according to claim 1 wherein said discharge ring is fastened to said hopper by radial webs.

5. Apparatus according to claim 1 characterized by cans for heating the gases leaving the finishing furnace and prior to their introduction into the shaft furnace.

6. Apparatus for heat treating bulk material, said apparatus comprising an annular shaft furnace for preliminary heat treatment of said bulk material; a finishing furnace to which said pretreated bulk material is fed for final treatment therein, said finishing furnace being a rotary furnace; said shaft furnace having an annular outer casing and a substantially cylindrical furnace core portion provided at its lower end with an outwardly diverging'conical surface, said casing and said core portion defining an annular shaft furnace space therebetween in which the bulk material is preliminarily treated by gases entering through the lower open end of said annular space and flowing upwardly in counter current to the flow of the bulk material; a discharge ring concentrically arranged to the axis of said shaft furnace and at a distance from said lower open end, said discharge ring serving as a support for the column of bulk mate- .rial moving through said annular shaft furnace space and along said conical core surface; means for conducting gases from said finishing furnace to a space surrounding the exposed surface of that portion of said bulk material column resting on said conical core surface; means for effecting relative movement between said discharge ring and at least one of the two parts defining said annular shaft furnace space; a substantially funnel shaped'discharge hopper located below said discharge ring and fastened thereto, the upper end of said hopper having an inner diameter larger than the outer diameter of said discharge ring, so as to provide a passage through which material discharged from the outer edge of said discharge ring'by said relative movement falls into said hopper; and conduit means connected to the lower end of said hopper through which said preliminarily treated bulk material passes into said finishing furnace.

7. Apparatus according to claim 6 wherein said discharge ring has a circular opening located below said shaft furnace core for dividing the flow of material from said discharge ring into two concentric streams.

8. Apparatus according to claim 7 wherein said annular discharge ring is provided with a circular protrusion of wedge shaped cross section to facilitate division of discharged material into said two streams.

9. Apparatus for heat treating bulk material, said apparatus comprising an annular shaft furnace for preliminary heat treatment of said bulk material; a finishing furnace to which said pretreated bulk material is fed for final treatment therein, said finishing furnace being a second annular shaft furnace concentrically located below said first mentioned annular shaft furnace; said first mentioned shaft furnace having an annular outer casing and a furnace core defining an annular shaft furnace space therebetween in which the bulk material is preliminarily treated by gases entering through the lower open end of said annular space and flowing upwardly in counter current to the descending bulk material column; a discharge ring concentrically arranged to the axis of said shaft furnace and at a distance from said lower open end, said discharge ring serving as support for the column of bulk material descending by gravity through said annular shaft furnace space; means for conducting gases from said finishing furnace to a space surrounding the exposed surface of that portion of said bulk material column disposed between said lower open end and said discharge ring; means for effecting relative movement between said discharge ring and at least one of the two parts defining said annular shaft furnace space of said first mentioned shaft furnace; a substantially funnel shaped discharge hopper located below said discharge ring and fastened thereto, the upper end of said hopper having an inner diameter larger than the outer diameter of said discharge ring, so as to provide a passage through which material discharged from the outer edge of said discharge ring by said relative movement.

falls into said hopper; and conduit means connected to the lower end of said hopper through which said prelimi- 6 narily treated bulk material passes into said finishing furnace.

10. Apparatus according to claim 9 characterized by means for heating the gases leaving the second shaft furnace prior to their introduction into said first mentioned shaft furnace.

11. Apparatus for heat treating bulk material, said apparatus comprising an annular shaft furnace for preliminary heat treatment of said bulk material; a finishing furnace to which said pretreated bulk material is fed for final treatment therein, said finishing furnace being a rotary furnace; said shaft furnace having an annular rotatably mounted outer casing and a substantially cylindrical furnace core portion provided at its lower end with an outwardly diverging conical surface, said casing and said core portion defining an annular shaft furnace space therebetween in which the bulk material is preliminarily treated by gases entering through the lower open end of said annular space and flowing upwardly in counter current to the flow of the bulk material; a discharge ring connected to the lower end of said conical core portion, said discharge ring serving as a support for the column of bulk material descending by gravity through said annular shaft furnace space and along said conical core surface; means for conducting gases from said finishing furnace to a space surrounding the exposed surface of that portion of said bulk material column resting on said conical core section; a substantially funnel shaped discharge hopper located below said discharge ring and fastened thereto, the upper end of said hopper having an inner diameter larger than the outer diameter of said discharge ring, so as to provide a passage through which material discharged from the outer edge of said discharge ring by the rotative movement of said outer casing falls into said hopper, and conduit means connecting to the lower end of said hopper through which said preliminarily treated bulk material passes into said finishing furnace.

References Cited in the file of this patent UNITED STATES PATENTS 341,035 Meech May 4, 1886 1,605,279 Pike Nov. 2, 1926 1,957,138 Hasselbach May 1, 1934 

